We have recently developed an MRI technique to image the glycosaminglycan (GAG) content of cartilage, and have demonstrated that it can serve as a surrogate for biochemical and histological evaluation of the tissue GAG. The main challenge being addressed by this R21 proposal is to obtain pilot data to determine whether this MRI technique can be used to predict the mechanical properties of the tissue. This represents a novel and innovative approach which is a substantial departure from our previous work both in technical and scientific aspects. Direct correlation of MRI and mechanical testing is nontrivial technically-a major challenge, for example, is accurate registration of data obtained via mechanical testing at points on an articular surface with corresponding points in a three- dimensional MRI data set. The scientific basis for the correlation of biochemical properties within the tissue and surface mechanical properties is an area that has not yet been explored for articular cartilage. Therefore, the R21 mechanism is needed to establish pilot data on the feasibility of correlating the MRI and mechanical tests, and on the level of modeling which will be required to correlate these data. These pilot data are needed before a larger scale rational research plan can be formulated.